I was almost always left alone. I knew a guy who was bugged all the time. The difference between us was that I was quiet on the subway, dressed in a subdued fashion. Basically I was a square. He was not. Japanese cops profile people. I _think_ what it boiled down to was, I didn't look like the sort of person who might be carrying marijuana on their person, another difference between my friend and I :-) This could be extremely outdated information though, that was over two decades ago (thinking about moving back, if a no-longer-young person can somehow find work.)